1. Field of the Invention
The present invention relates to a device for controlling microwave power of a microwave oven and more particularly, to a device for controlling microwave power of the microwave oven having a simple structure.
2. Description of the Prior Arts
In general, an electric field room of a microwave oven is provided with a magnetron for generating microwave. First and second induction coils of a high voltage transformer are disposed on a bottom plate of the electric field room. A high voltage which is generated by a mutually induced operation of these coils is applied to the magnetron thereby to generate the microwave. Such microwave is irradiated toward an inside of a cooking chamber of the microwave oven through an irradiating tube, by which the food inside the cooking chamber is heated to be cooked.
Cooking time and the strength (i.e., the power) of microwave supplied thereto are controlled by adjusting a cooking mode suitable for cooking various foods which are inside the cooking chamber in accordance with the kind of the foods. Therefore, the microwave oven is provided with a timer for controlling the cooking time and a device for controlling the microwave power.
A control panel which controls an overall operation of the microwave oven is disposed on a portion of the front panel of the microwave oven. The timer and the controlling device are disposed on the control panel.
Meanwhile, in a conventional microwave oven the timer and the microwave power controlling device are disposed on the control panel using a separate bracket. FIG. 4 is a perspective view for showing the conventional microwave oven having the control panel. In the figure, reference numeral 100 indicates a microwave oven, 105 indicates a control panel, 110 indicates a knob for controlling the microwave power and 120 indicates a timer knob. FIG. 5 is a perspective view for showing a device for controlling the microwave power which is coupled to microwave power controlling knob 110 of the microwave oven as shown in FIG. 4. FIG. 6 is a schematic sectional view for showing an engaged state of a timer with the microwave power controlling device of FIG. 5. As shown in these figures, in a conventional microwave oven a knob hole 116 for fixing the microwave power controlling device and a knob hole 117 for fixing the timer knob structure are formed at a back plate 111. A knob shaft 118 coupled to a knob 110 of the microwave power controlling device is inserted into knob hole 116 of the microwave power controlling device, and a timer knob shaft 121 coupled to timer knob 120 is inserted into timer knob hole 117. Knob 110 of the microwave power controlling device and timer knob 120 are attached to control panel 105 to be exposed outside, so that a user can manually modulate them.
A microwave power controlling cam 113 is connected and secured to knob shaft 118 through microwave power controlling knob hole 116 of back plate 111. A circular gear portion is formed at a lower portion of cam 113 which is fixed by bracket 150. A plate spring 114 is provided between an inner surface of bracket 150 and cam 113 to rotatably support cam 113. The gear portion of cam 113 is connected to timer 125 through a connection rack 112. Connection rack 112 has a "d" shape and a first rack portion 112A which is formed on an inner surface of a closed curved line and a second rack portion 112B which is formed on an extension of the enclosed curved line. First rack portion 112A is meshed with the gear portion of cam 113, and second rack gear portion 112B is meshed with a microwave power controlling circuit gear 126 of timer 125. Timer 125 is provided with a time circuit and a microwave power controlling circuit for controlling the microwave power of the microwave oven. The microwave power is controlled by changing the position of microwave power controlling circuit gear 126.
When microwave power controlling knob 110 is manually rotated in view of the user's necessity, the rotating force of microwave power controlling knob 110 is transmitted to cam 113 which drives connection rack 112 through the connection gear portion to straightly move connection rack 112. The driving force of connection rack 112 is transmitted to microwave power controlling circuit gear 126 of timer 125 having the microwave power controlling circuit to locate microwave power controlling circuit gear 126 at a predetermined position, so that the desired microwave power may be obtained.
The microwave power controlling device attached to the conventional microwave oven has numerous components such as bracket 150, plate spring 114, cam 113 and connection rack 112, and also includes back plate 111 for fixing the microwave power controlling device and timer 125. Due to the numerous components, the production cost increases and many steps for assembling them are necessary. Further, there are some difficulties in manufacturing the microwave power controlling device due to the complicated structure of the connection rack.